The present invention relates to a process and an apparatus for stripping insulated wires, particularly multistrand electric wires.
To reduce the time spent in interconnecting components with insulated wires, wire sections cut to a standard length are widely used, whose end portions are stripped over an appropriate length. Rotary-knife apparatuses exist for preparing such wires with stripped ends; they typically have knives which continuously rotate and whose spacing may be controlled. The knives are spread apart to introduce the required length of wire to be stripped, then moved toward each other to make a cut in the insulator up to the core of the wire; then the wire is pulled so as to remove the fragment of insulating sheath covering the part to be stripped and which is retained by the knives.
That approach has shortcomings. The rotary knives which retain the detached insulating fragment often damage the stripped metal core during removal of the wire, for the core cannot be maintained strictly along the axis of rotation of the knives during extraction of the wire. Those present-day machines which are automatic in operation prepare, from a coil of wire, sections of constant length with stripped ends. To change the length of the sections, the adjustment of the machine must be modified. Thus stocks of sections of different lengths are obtained, separated from each other. The operator must subsequently select a wire section of appropriate length. The stripped ends of multistrand wires may untwist.
It is an object of the invention to provide an improved process and apparatus for locally stripping insulated wires. It is a more specific object to overcome the risk of damaging the stripped part of the wires. It is still another object to provide an apparatus which is single in construction and operation and supplies a product more easily usable by a wiring operator.
A process for locally stripping insulated wires according to a first aspect of the invention comprises the steps of retaining the wire in guide means, cutting the insulation material with rotary knives over a fraction only of its thickness, bringing the knives at rest and pulling the wire for breaking the insulation material where cut.
A local stripping apparatus according to another aspect of the invention comprises a frame; a stripping head mounted on said frame for rotation about an axis; a wire guide carried by said head coaxially with said axis; a drive motor operatively associated with said head for rotating said head about said axis; a set of knives carried by said head and radially movable on said head toward said axis to a position where they define a gap less than the diameter of a wire passage in said wire guide and away from said axis; a unit for axially moving a wire projecting through said guide comprising an axially movable member, electrically controlled wire-clamping means carried by said axially movable member; and control means for successively actuating said clamping means for engaging said wire, axially moving said clamping means over a predetermined length, closing and rotating said knives to cut the insulating material over a fraction of its thickness stopping said drive motor and axially moving back said clamping means to tension the wire and break the remaining thickness of the insulating material where partially cut by the knives.
The invention will be better understood from the following description of a particular embodiment, given by way of example. The description refers to the accompanying drawings.